They look for all the world like a collection of flowers bursting into life.
Yet in fact, these are microscopic crystals grown in a Harvard laboratory.
Measuring just microns across, they were created to assemble themselves a molecule at a time.
The team say the work, carried out on glass slides, is able to control the process of crystal growth so precisely it can create curved and delicate shapes, that don’t resemble the cubic or jagged forms normally associated with crystals.
“Rather, fields of carnations and marigolds seem to bloom from the surface of a submerged glass slide, assembling themselves a molecule at a time,” the team say.
“For at least 200 years, people have been intrigued by how complex shapes could have evolved in nature.
“This work helps to demonstrate what’s possible just through environmental, chemical changes,” said Wim L. Noorduin of the Harvard School of Engineering and Applied Sciences (SEAS) and lead author of the paper in the journal Science.
By simply manipulating chemical gradients in a beaker of flui the team was able to create different “flowers”.
The shape of the crystals depends on a reaction of compounds that are diffusing through a liquid solution.
The crystals grow toward or away from certain chemical gradients as the pH of the reaction shifts back and forth.
The conditions of the reaction dictate whether the structure resembles broad, radiating leaves, a thin stem, or a rosette of petals, the team say.
“It is not unusual for chemical gradients to influence growth in nature; for example, delicately curved marine shells form from calcium carbonate under water, and gradients of signaling molecules in a human embryo help set up the plan for the body,” they say.
“You can really collaborate with the self-assembly process,” says Noorduin.
“The precipitation happens spontaneously, but if you want to change something then you can just manipulate the conditions of the reaction and sculpt the forms while they’re growing.”
Increasing the concentration of carbon dioxide, for instance, helps to create “broad-leafed” structures.
Reversing the pH gradient at the right moment can create curved, ruffled structures.
Noorduin and his colleagues have grown the crystals on glass slides and metal blades; they’ve even grown a field of flowers in front of President Lincoln’s seat on a one-cent coin. …
Harvard biologist Howard Berg has shown that bacteria living in colonies can sense and react to plumes of chemicals from one another, which causes them to grow, as a colony, into intricate geometric patterns.
Replicating this type of effect in the laboratory was a matter of identifying a suitable chemical reaction and testing, again and again, how variables like the pH, temperature, and exposure to air might affect the nanoscale structures….
Some see the complexity and beauty of nature and conclude an intelligent designer. Others note that environmental variation and small local chemical interactions which follow the laws of physics result in self-organizing systems forming patterns we recognize as life. The duties of our deities are reduced, year by year.